Interestingly, the above derivation also gives an alternative, simple proof of the main result of Ref. [1]}. In fact, an intermediate technical result in the proof of Theorem REF  is
that in the presence of the operational features O1-O2,
noncontextual models must have a direct relation between the experimentally accessible confusabilities \(c_{ss^{\prime }} = p(M_{s^{\prime }}|P_s)\)  and the \(\ell _1\)  distance between the corresponding probability distributions:
\(\Vert  \mu _s - \mu _{s^{\prime }} \Vert  = 2(1- c_{ss^{\prime }}).\) 
